1. Field of the Invention
The present invention relates to mufflers for use with small engines, such as engines of the type used with lawnmowers, lawn tractors, and other lawn and garden implements, as will as in sport vehicles.
2. Description of the Related Art
Typically, mufflers used with small engines are attached directly to the exhaust port or ports of the engine cylinder head, or alternatively, may be mounted remotely from the engine and attached to the exhaust port or ports of the engine cylinder head by one or more exhaust pipes communicating exhaust gasses from the cylinder head to the muffler. The construction of such mufflers varies greatly. However, such mufflers often include a muffler shell having a muffler tube disposed therein, the muffler tube having a plurality of holes for silencing the noise associated with the exhaust gasses. The exhaust gasses typically exit the muffler either through an open end of the muffler tube or through holes or slots in the muffler shell.
Some exhaust systems have additionally included exhaust tuning features to enhance engine performance in addition to reducing exhaust noise. For example, one method of exhaust tuning involves the use of a straight, elongated exhaust pipe which includes an area of expanding cross section, allowing the exhaust gasses to expand when passing therethrough. In this manner, when the exhaust gasses encounter the area of expanding cross section of the exhaust pipe, the expanding of the pressure waves associated with the exhaust gasses reflect negative pressure waves back toward the exhaust port. These reflected, negative pressure waves aid in scavenging exhaust gasses from the combustion chamber of the cylinder through the exhaust port, which in turn allows a greater amount of air/fuel combustion mixture to enter the combustion chamber to enhance engine performance.
Problematically, such tuned exhaust systems often require very lengthy straight exhaust piping, which is not practical for use in the mufflers of smaller engines because such engines are designed to be compact in size.
What is needed is a compact muffler for use in small engines, such as those used in the lawn and garden industry, which includes exhaust tuning features to enhance engine performance and provide improved exhaust noise reduction.